[sdiy] Simple FM input (and tricks...)

[cheater cheater]

Justin,
buffering might prove to create problems if you want to create FM
feedback loops, either from the VCO to itself, or between 2 VCOs.

As you already have one VCO, try and see what happens when you make it
FM itself. Then try the same with a buffer - and report. I'm very
interested in the outcome of this :)

Cheers

On Sat, Aug 2, 2008 at 2:03 PM, Justin Owen <juzowen at googlemail.com> wrote:
> Hey all,
>
> The first of a run of questions this weekend...
>
> I've recently added a simple FM input to my current VCO. It's basically just an op-amp summer - the first input is a pot set up as a voltage divider for Pitch CV and the second input is for an external sound source.
>
> I'm not trying to re-invent the DX7 - I'm just enjoying all the nice metallic tones - and of course all the great space noises!
>
> But... I was wondering if there'd be any advantage to adding a 'stage' of some sort between the external audio/FM input and the summing op-amp? Something like a simple buffer stage - or maybe even gain?
>
> The reason I'm asking is because, while this build will only have an external sound source at something approaching 'line level' for FM - future builds might have sources at different levels/impedances - so I thought it might make sense to try and match the different inputs a little closer - before they enter the summing stage.
>
> Does this make sense? Is there any advantage to adding something?
>
> Cheers much
>
> Juz
>
>
>
>
>
>
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